The present invention relates to a light-illuminating rod, and in more detail to a light-illuminating rod comprising a rod member which is made of a flexible plastics and which can pipe the light allowed to impinge on one end thereof in the longitudinal direction toward the other end thereof, and a diffusible reflective film fixedly bonded to the surface thereof, and capable of being"" advantageously utilized as a linear illuminator. The light-illuminating rod can be handled while being deflected, and it may be fixedly installed in a deflected state.
It has heretofore been known to utilize a light-illuminating rod having a rod member capable of piping light allowed to impinge on one end in the longitudinal direction, toward the other end, and a light diffusible reflective film which is fixedly bonded to the rod member to cover part of the surface thereof and which is arranged along the longitudinal direction thereof as a linear illuminator in place of a conventional illuminator such as a fluorescent lamp. In the light-illuminating rod, usually, a light source is arranged on one end of the rod member so that light is capable of impinging on the end toward the interior thereof Illumination light is then irradiated from the side surface of the rod member, which is a light-irradiating surface located opposite to the bond surface of the light diffusible reflective film, over about the whole area in the longitudinal direction thereof. Such a light-illuminating rod overcomes, for example, one of the problems that a vacuum discharge glass tube such as a fluorescent tube has, namely a problem of being easily broken.
Light-illuminating rods will be explained by making reference to Japanese Patent Publications, etc. which disclose them.
Japanese Examined Patent Publication (Kokoku) No. 4-70604 (Japanese Unexamined Patent Publication (Kokai) No. 60-11806) and Japanese Examined Patent Publication (Kokoku) No. 1-58482 (Japanese Unexamined Patent Publication (Kokai) No. 61-93409):
Relatively rigid materials such as quartz glass having a refractive index of 1.46, optical glass having a refractive index of 1.5 to 1.7 and a silicone resin having a refractive index of 1.41 are used as rod member materials of the light-illuminating rods disclosed in these Patent Publications. The light diffusible reflective film (sometimes termed diffusible film hereinafter) is prepared by dispersing fine powder (light diffusible reflective particles) having a higher refractive index than the rod member in a binder consisting of a light-transmittable polymer and mixing them. The diffusible film is placed in a stripe form on the outer periphery of the rod member along the longitudinal direction. The light-illuminating rod is used in place of a linear fluorescent tube. Accordingly, it is not intended to be used while being deflected or bent.
The rod member is solid. Fine powder of a material such as barium sulfate having a refractive index of 1.51, magnesia having a refractive index of 1.8 or titania having a refractive index of 2.6 is used as the fine powder for the diffusible film. The binder is restricted to a silicon rubber or silicone resin both having a refractive index of 1.41. That is, the refractive indexes of materials of the diffusible films disclosed herein have the following relationships: the refractive index of any of the binders is up to that of the corresponding rod member, and the refractive index of the diffusible reflective particles is higher than that of the corresponding rod member. On the other hand, when a silicone rubber is used as the binder, vulcanization is conducted to improve the heat resistance, light resistance, durability, peel resistance, etc.
Japanese Unexamined Patent Publication (Kokai) No. 62-142465, Japanese Examined Patent Publication (Kokoku) No. 7-3553 (Japanese Unexamined Patent Publication (Kokai) No. 63-108332) and Japanese Unexamined-Utility model Publication (Kokai) No. 4-104603:
The light source disclosed in the Publications each have substantially the same light-illuminating rod as disclosed in the above Publications comprising a diffusible film and a rod member, and such a unit in combination as a converging unit for enhancing the illumination efficiency (e.g., a rod lens), a reflection mirror having slits at light-irradiating portions and a diffusible reflective layer provided on the light-exiting end surface.
Japanese Unexamined Utility Model Publication (Kokai) No. 63-146803:
The light-illuminating rod disclosed in the Utility Model Publication has substantially the same rod member as disclosed in the Publications mentioned above, and a recessed portion is provided as a light diffusible portion, in parallel with the axis of the rod member on the outer periphery thereof. Light diffusible material comprising titanium dioxide and a silicone resin is placed in the recessed portion. A quantity of light reaching the -light diffusible portion thus increases, and linear illumination can be conducted with great efficiency.
Japanese Unexamined Utility Model Publication (Kokai) No. 54104:
The Utility Model Publication discloses a UV light source unit, and restricts the light impinging on the light-piping rod to UV-rays. Substantially the same material as in the Patent Publications mentioned above is used as the rod member. The diffusible film is formed from such fine powder which absorbs less light in the UV-ray wavelength region as aluminum oxide powder, and silicone resin. As a result, light generation in an irregular quantity can be prevented.
Japanese Unexamined Utility model Publication (Kokai) No. 6-21940:
The linear light source unit disclosed in the Utility Model Publication is characterized by that the rod member and the light source are integrated in a stick form. A rod member made of polymethyl methacrylate (PMMA) is disclosed therein, and acrylic resin is mentioned as an appropriate binder for the diffusible film for the rod member. However, the rod member made of PMMA and used for the light source unit has a poor flexibility. Accordingly, the light source unit can be used only for restricted applications such as copying machines. Moreover, the Utility Model Publication discloses no detail related to the acrylic resin as a binder. In addition, the glass transition temperature (Tg) of the PMMA used in the rod member is approximately 100xc2x0 C.
As illustrated above, light-illuminating rods of various types have been known. However, rod members used as the cores of conventional light-illuminating rods have no flexibility at all, or have a flexibility not sufficient for handling while being deflected or installing while being in a bent state. Accordingly, there is no such a case where diffusible films Used in combination with the rod members are improved so that the diffusible films can follow the deflection of the rod members. For example, when a vulcanized rubber is used as a binder of the diffusible films, the vulcanized rubber usually has a relatively high Young""s modulus of about 108 dyne/cm2 (about 100 Mpa). As a result, a bonded diffusible film formed from the vulcanized rubber has relatively poor follow-up properties in accordance with the deflection of the rod members. The light-illuminating rods in which acrylic plastics-containing flexible rod members are used and which have been put to practical use in recent years may be handled while being deflected or fixedly installed while being bent. The conventional diffusible films as mentioned above, however, are not satisfactory in respect to adhesion to the flexible rod members and flexibility.
An object of the present invention is to solve the problems associated with the prior art as mentioned above, and improve the adhesion and flexibility of the diffusible film in the light-illuminating rod capable of being used as a linear illuminator so that the rod may be handled while being deflected and fixedly installed while being bent.
According to the present-invention, the object as mentioned above can be achieved as described below. In a light-illuminating rod comprising (a) a flexible rod member formed from a light-piping plastic material and (b) a light diffilsible reflective film which is fixedly bonded to part of the outer periphery of the rod member along the longitudinal direction thereof and which comprises (i) a light-transmittable polymer and (xe2x88x92ii) light diffusible reflective particles dispersed in the polymer,
said light diffusible reflective film is formed by using a light-transmittable polymer having a storage modulus of 1.0xc3x97104 to 1.0xc3x97108 dyne/cm2 as measured by a viscoelastic spectrometer.
In the light-illuminating rod of the present invention, the light diffusible reflective film is fixedly bonded to the surface of a flexible rod member forming the core of the rod, and the light diffusible reflective film is formed from a composition prepared by dispersing light diffusible reflective particles in the light-transmittable polymer having a storage modulus of 1.0xc3x97104 to 1.0xc3x97108 dyne/cm2 and mixing them. As a result, the adhesion and flexibility of the diffusible film are improved, and consequently the follow-up properties of the diffusible film in accordance with the deflection of the rod member are improved.